In recent years, there have been many cases where a punching device is used in combination with a monochrome and color copying machine, a printer or the like. According to this type of punching device, it receives a sheet of paper recorded with an image, and punches holes at the downstream side of the sheet of paper utilizing its punching function. The sheets of punched paper are re-aligned to one another, and are automatically subject to bounding processing such as ring binding by utilizing the holes. For two-hole file or the like, a method how to file them by hands is also employed.
Further, in a general reciprocal punching device, a sheet of paper temporality stops at a punch-processing section before it is punched. At this time, a method how to detect an end portion of the sheet of paper by a sensor on the transferring way thereof and to correct an amount of its transfer to the punching position is employed. There may be a case where a sheet-reversing function is employed for transferring these sheets of paper.
A configuration of a post-processing apparatus according to a conventional example is shown in FIG. 25. The post-processing apparatus 200 shown in FIG. 25 is configured to contain a paper transfer path 1, a punch-processing section 2, a binder-paper-aligning unit 33, a binding unit 4, a transfer belt 5, a discharge stack 6, and an apparatus main body section 7.
The paper transfer path 1 is located within the apparatus main body section 7, and a switchback roller is provided at one side thereof. The punch-processing section 2 is located below the paper transfer path 1, and a sheet of printed paper 3 fed to the paper transfer path 1 is switched on the traveling direction thereof by the switchback roller. After that, it makes a U-turn and is transferred to the punch-processing section 2.
At the punch-processing section 2, it is configured so that the sheet of paper is punched at the front end thereof in its transfer direction in order to transfer and discharge the sheet of paper under its face-down printing. Below the punch-processing section 2, the binder-paper-aligning unit 33 and the binding unit 4 are located as well as the sheet of punched paper 3 makes a U (an R)-turn and is transferred to the binder-paper-aligning unit 33. In the binder-paper-aligning unit 33, a plurality of sheets of paper 3 are aligned and when a predetermined number of sheets of paper have been aligned, a stack of sheets of paper with the holes punched at the side of binding unit 4 is inclined, and the stack of sheets of paper at this inclined position is bound by a binding member.
A transfer belt 5 and a discharge stack 6 are located at the downstream side of the binder-paper-aligning unit 33 and the stack of sheets of paper (hereinafter, referred to as a booklet 90) bound by a binding member is transferred on the transfer belt 5 and is discharged to the discharge stack 6. In this manner, such a mechanism is employed that the sheet of paper 3 is reversed (from its rear end to its front end), is transferred through the U-turn transfer path to the punch-processing section 2, and is then returned through the U-turn transfer path to the binder-paper-aligning unit 33 (i.e. S-shaped transfer route).
It is to be noted that Japanese Patent Application Publication No. S59-97957 has disclosed a sheet-reverse-dealing apparatus. According to this sheet-reverse-dealing apparatus, it is configured so that when a sheet transferred in a positive direction is reversed and its forwarding direction is switched to be returned to the transfer path, the transfer speed of the sheet after the forwarding direction of the sheet has been switched is set to be faster than the transfer speed of the sheet in the positive direction. According to this configuration of this device, the sheet when being reversed can be transferred at higher speed.
Japanese Utility Model Publication No. H05-25838 has disclosed a punching device. According to this punching device, a flexible plate-like member is provided on a dice on which an item to be punched is placed, and the plate-like member is always pressed onto a side of the dice. It is configured so that when the item to be punched is set during the punching thereof, the flexible plate-like member biases the item to be punched toward the side of the dice. Thus configured apparatus is capable of preventing the item to be punched from isolating from the dice when punched.
Further, Japanese Patent No. H09-2575668 has disclosed a paper-accommodating apparatus. According to this paper-accommodating apparatus, matching means is provided within a tray and in a case of, by a transfer roller, exerting a transfer force to a front corner portion of a sheet of paper to be accommodated in the tray, the paper transfer force exerted by the matching means is set to be smaller than the paper transfer force exerted by the transfer roller. Thus configured apparatus avoids the sheet of paper being made free, and thus, a risk of skew thereof is eliminated.
However, according to a punching device used in combination with a copying machine, a printer, or the like, there are any following problems.
i. The punching device of a conventional scheme shown in Japanese Utility Model Publication No. H05-25838 punches holes in a sheet of paper being transferred at its downstream, in many cases. Contrary to this, in view of the case where holes are punched in a sheet of paper at a side of its upstream utilizing the sheet-reversing function as shown in Japanese Patent Application Publication No. S59-97957 (on page 2) and the punching operation is achieved by having the sheet of paper struck thereagainst utilizing any transferring force, a reference in the sheet of paper and the position to be punched become opposite to each other, so that there is a risk that accuracy of punching position is lowered due to variations in paper sizes and mechanical errors.
ii. Further, in realizing a basic operation of re-aligning sheets of the paper to one another after they have been punched and performing automatic binding on them by utilizing the punched holes, if the punching method of a conventional scheme is employed as it is, there is a risk that accuracy of hole position becomes low and the hole positions of the aligned sheets of paper deviate from one another, and an automatic binding operation is hindered.
iii. In a general type of the reciprocal punching device, it is required to temporally stop a sheet of paper before punching it. At this time, in order to improve accuracy of the hole positions, a method where an end portion of the sheet of paper is detected by a sensor while transferred and an amount of the transfer thereof up to the punching position is corrected is employed. However, in the actual situation, the correction cannot cover the error in the amount of transfer after the detection and the skew in the sheet of paper. Therefore, high accuracy of hole positions is not achieved.
Incidentally, although it is conceivable to employ a method where a fence as a reference is provided in the vicinity of the punching position in order to improve accuracy of the hole positions and to strike a sheet of paper thereagainst, if striking the sheet of paper against the fence at high speed, there is a risk that the paper is flawed.
Further, if a binding apparatus is constituted as one shown in FIG. 25 by combining the sheet reverse function shown in Japanese Patent Application Publication No. S59-97957 with the punching device shown in Japanese Utility Model Publication No. H05-25838, there are following problems.
i. Since a mechanism where a sheet of paper 3 is reversed to be transferred through the U-turn transfer path to the punch-processing section 2 and after that, it is again returned through the U-turn transfer path to the binder-paper-aligning unit 33 is employed, the moving distances of the sheet of paper 3 and the booklet 90 are inevitably set to long.
ii. On the U-turn transfer path and the R-shaped transfer path at low temperature in a dry state, the rigidity of the sheet of paper 3 increases and the sliding resistance thereof increases accordingly so that a rate of occurrence of paper jamming increases (especially, when the paper is thick) or an ability to release paper jamming deteriorates (it is hard to access to the jammed paper by hand). Therefore, there is a risk that high manufacturing cost is required and transferability of the paper folded into the shape of the letter Z deteriorates.
iii. According to the binding apparatus 200 provided with a U-turn transfer path or an R-shaped transfer path, a period of running time of a motor becomes long so that the durability of the motor deteriorates and power consumption by the motor becomes large.
iv. If a paper transfer path accompanying with a U-turn transfer path is installed, a space for the curvature thereof is needed so that a width of the apparatus main body becomes large, thereby resulting in hindrance to make the binding apparatus 200 compact in size.
v. Further, according to the booklet-discharging system shown in FIG. 25, the booklet 90 is horizontally transferred on the transfer belt 5 and is discharged to the discharge stack 6. Since this mechanism is one of the factors of the increased width of the apparatus main body, in view of a mechanism where the booklet 90 is transferred obliquely, for example, when claws are attached to both of two belts and a moving amount of each of the belts is controlled to transfer the booklet while being held by the claws, if the belt claws are hit at high speed against the booklet constituting a large number of sheets of paper and thus heavy in weight, there is a risk that the motor becomes out of order caused by the impact load thereof.